稻曲病菌离体培养体系的构建与优化

稻曲病是水稻穗期的一种重要病害，严重影响稻米的产量和品质。稻曲病菌Ustilaginoidea virens 在离体培养条件下生长缓慢，严重制约了杀菌剂室内生测试验的观察和高效筛选。本研究以稻曲病菌培养基为研究对象，通过筛选、组合和优化固体培养体系的氮源、碳源、凝固剂以及阳离子浓度，以期构建适合稻曲病菌生长的室内培养体系。结果发现:在5种常见的商品化培养基中，稻曲病菌的生长速率仅为0.7~2.3 mm/d；而在18种配制培养基中，有77%的培养基对稻曲病菌表现出不同程度的生长促进效应，其中蛋白胨蔗糖结冷胶 (PSGG) 培养基的促进效果最显著 (P < 0.05)，生长速率达3.4 mm/d，且其对不同地理分布的稻曲病菌菌株均有生长促进效应。此外，在以结冷胶作为凝固剂的培养基中添加质量分数为0.02%的硫酸镁 (Mg2+)，可有效提高培养基的凝固程度，且对菌丝体的生长速率无影响。在适合稻曲病菌生长的PSGG培养基中，蛋白胨和蔗糖是合适的氮源和碳源组合，结冷胶是合适的凝固剂。此研究结果可提高室内培养稻曲病菌的生长速率，为进一步理解稻曲病菌在离体条件下的生长机制及提高室内杀菌剂生测试验的效率提供了重要参考。

Construction and optimization of a culture system for growth and bioassay of Ustilaginoidea virens in vitro

Rice false smut is an important fungal disease at the rice heading stage, which causes severe loss to yield production and rice quality. Due to insufficient growth performance of Ustilaginoidea virens in vitro, screening and observation of effective fungicides in bioassay have been restricted. In this work, selection, combination and optimization of various carbon, nitrogen sources and coagulants have been carried out, an optimized culture system for U. virens growth was developed. The growth rate of U. virens in 5 representative types of commercial media was only from 0.7 to 2.3 mm/d, while the significant growth promotion effect on U. virens was observed in 77% of 18 types of compound media. Especially, maximum growth rate of 3.4 mm/d was observed in the peptone sucrose gellan gum (PSGG) medium. Interestingly, growth promotion effect of this medium was also observed on different strains of U. virens collected from rice grown in geographically diverse regions. Moreover, supplementation of 0.02% MgSO₄ into the media solidified using gellan gum could enhance the solidification degree of the culture system, but did not affect the growth of U. virens. This indicated that peptone and sucrose were ideal nitrogen and carbon sources, respectively, in the PSGG medium, and gellan gum was a favorable coagulant. Our results would improve the growth rate of U. virens in vitro, and advance the understanding of underlying mechanism involved in the growth of U. virens, and also serve as an basis for the efficiency improvement of the bioassay system for U. virens.